The present invention relates to paperboard packaging material and packages constructed therefrom, and more particularly to an improvement in applicant's prior U.S. Pat. No. 4,914,266 relating to susceptor packaging for heating and browning foods in a microwave oven.
One of the problems associated with the use of microwave energy for cooking is that it fails to brown and crisp those foods which are normally expected to have such a quality. Applicant's prior U.S. Pat. No. 4,914,266, entitled "Press Applied Susceptor for Controlled Microwave Heating", addressed that problem and provided a susceptor packaging material that was useful for the intended purpose. According to applicant's prior patent, it was discovered that both carbon and graphite (i.e., conductive carbon materials), were available in particle sizes which could be readily dispersed into solvent based inks. Moreover, it was found that inks incorporating these materials could be printed on coated or uncoated paperboard in any prescribed pattern with known printing methods and equipment, including gravure and flexography. Furthermore, by overprinting the desired patterns, or by varying the concentration of the carbon susceptor material within the prescribed pattern, the concentration of susceptor material applied in the prescribed pattern could be controlled to obtain useful time-temperature profiles for the most effective browning of different kinds of food. The packaging material manufactured could then be converted into any desired package shape using conventional methods. The performance of such packages was found to be comparable to metallized aluminum susceptors in the generation of heat for browning during microwave cooking. However, the susceptor-ink compositions disclosed in applicant's prior patent had a tendency to char or burn at elevated temperatures when no food was in the packages much like some of the susceptor packaging that use metallized aluminum. Also, the susceptor-ink compositions proved to be difficult to keep in place on the surface of some paperboard, thus causing potential contamination problems. Accordingly the present invention was developed to overcome those problems and to provide susceptor packaging material of improved quality.